This invention relates to explosion resistant covers for battery containers.
Storage batteries generate internal gases when in use and these gases, such as hydrogen and oxygen, are usually vented to the ambient atmosphere in order to relieve internal battery pressure. However, this venting of gases can create an explosion hazzard if a spark occurs near the battery when the gas is being discharged. The spark ignites the gas, and the flame or spark travels back into the battery whereupon the battery explodes. Hence, it is desirable to provide a battery cover design and battery which eliminates or minimizes these explosions.
It is desirable also to provide a maintenance free battery cover design which provides a flat battery top surface but which allows continuation of existing manufacturing techniques for the battery case and filling of the battery with electrolyte while at the same time allowing for venting of gases without the hazard of explosion as aforementioned.
Examples of patents relating to anti-explosion battery vents and caps are the Godshalk Patent, U.S. Pat. No. 3,992,226 entitled, "Anti-Explosion Cap For Storage Batteries", and the Schaumburg patent, U.S. Pat. No. 4,010,044 entitled, "Battery Vent".
With respect to maintenance free cover designs, the Badger patent, U.S. Pat. No. 3,904,441 entitled, "Battery Vent Construction", at column 2, relates to a battery cover which has a longitudinal channel extending across its length with a plurality of spaced apart apertures each leading to a battery cell. An elongate acid proof gasket having a plurality of openings is positioned to coincide with the apertures in the cover and is adhesively bound to the middle of the channel. A strip of micro-porous filter material is adhesively secured to a rigid elongate guard which extends along the length of the battery cover within the channel. The guard is equipped with a plurality of spaced apart platforms or spacers which are adhesively secured to the adjacent gasket to hold the guard in place. The guard is equipped with a continuous downwardly extending lip on both ends and sides of the guard. Gas is allowed to escape from the battery through the micro-porous material and spaces between the platforms or spacers and then out between the guard lip and side walls of the channel.
The Miller patent, U.S. Pat. No. 3,802,597 entitled, "Battery Container Cover", discloses a cover body formed with a row of well portions sunk below the top plane of the cover. Each well portion defines a cell opening closed by a vent plug. A flat cover strip is sealed over the well portions so as to be substantially contiguous with the top cover surface. The cover strip is fitted onto a ledge formed in the cover body below the upper surface of the cover. A plurality of spaced lugs are formed in the ledge defining fusing points for securing the strip on to the body. The strip is slightly smaller than the outer periphery of the ledge. The strip is centered on the ledge and pressed and sealed in place at the locations of the lugs. Gas escapes through the well portions and beneath and around the edges of the cover strip. This is described in column 2 of the patent.
Also, the Sabatino patent U.S. Pat. No. 4,037,030 is directed to a maintenance free battery.
Some battery manufacturers provide a battery cover with an elongate channel along its length having a plurality of spaced apart vent wells in the channel opening into the battery cells. Vent caps are provided to fill each well which allow gas to escape but prevent electrolyte from splashing out of the battery. A cover strip which fits within the channel is provided which firmly attaches to each of the caps. The strip is provided with a plurality of pairs of curved projections which extend from the underside of said strip. Each projection of each pair is disposed to mate with opposite sides of the curved periphery of a corresponding vent cap. The projections extend generally perpendicular from the strip. Each projection of each pair is equipped with a ledge on the concave face of the projection. This ledge is disposed to snap within a corresponding groove surrounding each vent cap. Thus, when the ledges of each pair are in place around a corresponding vent cap, the strip becomes locked in place in the channel. The vent caps engage two parallel line projections which run down the center of the strip on the underside. The vent caps are free to rotate because the grooves surround the cap but the strip cannot be easily removed from the caps.